Computer systems can receive user input using various techniques. For example, a computer system that includes a touchscreen display device can recognize gestures that a user performs across the touchscreen surface and, in response, can perform associated user input actions. An example gesture and action pair includes a user swiping a single finger across a touchscreen surface in order to pan the display in the direction of the swipe. Another example gesture includes a user pinching two fingers together on the touchscreen surface in order to zoom the display outwards.
Other user input techniques use object recognition operations. For example, a computing system may track the location and movement of an object through a series of frames of a video that is captured by a digital camera connected to the computing system. In some examples, such object tracking processes are used to track the movement of a user's face. The computer system can modify a visual display based on the movement of the user's face.